The present invention relates to a plasma processing apparatus and an operation method thereof of processing a board-shaped sample such as semiconductor wafer in a processing chamber provided in a vacuum container by plasma formed in the processing chamber and more particularly to such a plasma processing apparatus including a sample stage disposed in the processing chamber and on which a sample is placed and a plurality of pins disposed in the sample stage to move the sample up and down above the sample stage and an operation method of the plasma processing apparatus.
The above-mentioned plasma processing apparatus generally includes pins (hereinafter referred to as pusher pins) disposed in the sample stage having an upper surface on which the sample is put in order to place the wafer on the upper surface or separate off the wafer from the upper surface. Driving means for moving the pusher pins up and down may be air drive type or electric motor drive type.
Since the pusher pins are moved while being in contact with the sample, the pusher pins are usually disposed in a decompressed atmosphere. On the other hand, since the driving means is disposed within the atmosphere, sealing part is disposed between the driving means and the pusher pins to keep airtight. For example, there is a method in which axial sealing means using O-ring which abuts against the side of a cylindrical pusher pin to realize airtight sealing as a sealing face is disposed or the circumference of the pusher pin is covered with a bellows-structure member such as elastic bellows and sealing member is disposed therein to hermetically seal the inside of the sealing member from the outside in which driving means of the pusher pin is disposed. In the axial sealing method, a lubricating oil reservoir is sometimes provided in order to reduce a sliding resistance.
As prior arts using such a pusher pin, there are U.S. Pat. No. 6,646,857, JP-A-2002-305188 and U.S. Pat. No. 5,622,593.
U.S. Pat. No. 6,646,857 discloses that a plurality of pusher pins disposed within a sample stage are moved up and down to lift a sample such as semiconductor wafer absorbed onto the upper surface of the sample stage up and then down so that the sample is placed on the upper surface of the sample stage and the circumference of the pusher pins is covered with bellows. JP-A-2002-305188 and U.S. Pat. No. 5,622,593 disclose that a plurality of pusher pins are housed in a sample stage and a driving device for lifting a sample up and down is disposed out of a vacuum container similarly to U.S. Pat. No. 6,646,857.
In U.S. Pat. No. 5,622,593, gas having heat transmission characteristic such as helium (He) gas is fed between the sample placed on the upper surface of the sample stage and the upper surface of the sample stage in order to facilitate heat transmission therebetween, while there is shown the structure in which the gas having the heat transmission characteristic is introduced from an opening formed in an inner wall of a vertical hole of the sample stage in which the pusher pin is housed and is fed through the vertical hole into the rear side of the sample from an opening formed in the upper surface of the sample stage and in which the pusher pin comes in and out.